1. Field of the Invention
The present invention relates generally to the field of tannate chemistry and more specifically to methods for processing tannate suspensions.
2. Description of the Prior Art
The use of tannate suspensions for pharmaceutical use is well-known. U.S. Pat. No. 6,287,597 describes tannate suspensions containing pyrilamine tannate and phenylephrine tannate. The suspension is prepared in a conventional manner such that one teaspoon contains 30 mg pyrilamine tannate and 5 mg phenylephrine tannate with benzoic acid, coloring agent, natural and artificial flavors, glycerin, kaolin, magnesium aluminum silicate, methyl paraben, pectin, purified water, saccharin, sodium hydroxide and sucrose or sorbitol. The January 1990 issue of Annals of Allergy, Volume 64, describes combinations of chlorpheniramine tannate, pyrilamine tannate and phenylephrine tannate. An article in Clinical Medicine, dated September 1965, pages 1475–1478 describes tablets of pyrilamine tannate, chlorpheniramine tannate and amphetamine tannate. Phenylephrine tannate compositions are disclosed in U.S. Pat. No. 5,599,846 and phenylephrine tannate and chlorpheniramine tannate compositions are disclosed in U.S. Pat. No. 6,037,358. None of these references suggest or describe the production of a suspension by means of an in-situ conversion to the tannate salt of the active ingredient to provide a dosage form which affords a sustained release of the active ingredient over prolonged intervals of time. Such a suspension is needed to improve patient compliance with dosage requirements.